Age and fentanyl pharmacokinetics.

Fentanyl pharmacokinetics was compared in two groups of adult patients, one group (n = 5) aged less than 50 years, and one group (n = 4) aged greater than 60 years. Despite equivalent doses of fentanyl (10 microgram/kg IV), serum drug concentrations were significantly higher in the older patient group. This was reflected by a prolonged terminal elimination half-life in the elderly compared with the younger patients (945 versus 265 minutes, respectively, p less than 0.005). Volumes of the central compartment and volumes of drug distribution were similar in both patient groups. However, drug clearance was markedly decreased in the elderly (265 versus 991 ml/min, p less than 0.005). These data suggest that a given dose of fentanyl will be clinically effective for a longer period in older patients than in younger patients.